Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B47/00—Constructional features of components specially designed for boring or drilling machines; Accessories therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q11/00—Accessories fitted to machine tools for keeping tools or parts of the machine in good working condition or for cooling work; Safety devices specially combined with or arranged in, or specially adapted for use in connection with, machine tools
  • B23Q11/10—Arrangements for cooling or lubricating tools or work
  • B23Q11/1038—Arrangements for cooling or lubricating tools or work using cutting liquids with special characteristics, e.g. flow rate, quality
  • B23Q11/1053—Arrangements for cooling or lubricating tools or work using cutting liquids with special characteristics, e.g. flow rate, quality using the cutting liquid at specially selected temperatures
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T408/00—Cutting by use of rotating axially moving tool
  • Y10T408/03—Processes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T408/00—Cutting by use of rotating axially moving tool
  • Y10T408/44—Cutting by use of rotating axially moving tool with means to apply transient, fluent medium to work or product

Definitions

• the invention relates to a method for machining a workpiece with a machining tool, in particular for drilling or cutting, in which the machining zone is effectively cooled by means of a cryogenic mixture formed of liquid nitrogen and solid C0 2 particles, as well as on an installation for implementing this process.
• a cooling and / or lubricating compound typically water or oil, for example, is applied in contact with the machined zone or heating zone, which not only makes it possible to cool more or less efficiently. this area but also to lubricate it so as to improve the service life of the machining tool, to improve the dimensional accuracy and / or to reduce the surface roughness of the machined object.
• cooling compound and / or lubricant any body for cooling and possibly lubricating the parts or elements in contact, that is to say material and tool, and thus to reduce the temperature of the parts or elements considered, by example water or water vapor, oils, a gas ...
• the temperature decrease generated by the contact with the cooling compound also makes it possible to improve the machining parameters and thus to increase the overall productivity of the machining operation.
• cooling compounds and / or conventional lubricants are not effective enough to be able to effectively cool some hard materials, such as stainless steel at high machining speeds, during their machining because the heat produced by the friction of the tool on these hard materials is too important to be effectively absorbed by these conventional compounds.
• any chemical lubricant is prohibited because of surface contamination problems.
• EP-A-1580284 has also been proposed by EP-A-1580284 and also by the documents WO-A-9960079, EP-A-2155451 and EP-A-1775064, to use liquid nitrogen at atmospheric pressure as lubricating and cooling fluid during machining.
• the liquid nitrogen is at about -196 ° C and its cooling contribution is remarkable, which makes it a significantly better solution than the other gases proposed.
• the service life of a tungsten carbide cutting tool used to cut stainless steel at a speed of 100 m / min will be 3 to 4 times greater if using liquid nitrogen at atmospheric pressure in place of a standard lubricant, such as water or oil.
• liquid nitrogen is known to create a heating layer when it comes into contact with a warmer room, that is to say at a temperature above -196 ° C. The warmer the room, the higher the calefaction layer.
• the temperature difference between the liquid nitrogen and the workpiece can range, for example, from 500 to 1000 ° C.
• This heating layer consists of nitrogen gas which forms between the liquid nitrogen and the workpiece, a gaseous thermal barrier limiting the supply of frigories from liquid nitrogen.
• EP-A-1580284 relates to a method for improving the working surface of a tool during its shaping by injection of liquid nitrogen on the surface of the tool.
• the problem is to be able to improve the cooling by liquid nitrogen during a machining operation of a material, in particular the drilling or cutting of a hard material, such as carbon steel, stainless steel, aluminum and its alloys, or an alloy based on chromium and / or nickel, or titanium ...
• a hard material such as carbon steel, stainless steel, aluminum and its alloys, or an alloy based on chromium and / or nickel, or titanium ...
• the proposed solution is a method of machining a workpiece with a machining tool, in which at least a portion of the machining zone that can be heated during the machining of the workpiece is cooled.
• the machining tool distributing liquid nitrogen at said machining zone or the tool, characterized in that furthermore distributing C0 2 particles in solid form in the machining zone .
• the invention it is proposed to achieve a cooling of the machining area and / or the machining tool, that is to say the elements that heat up during the actual machining, by sending in contact with the machining zone and possibly the tool itself, solid particles mixed with a cryogenic fluid in the liquid state, that is to say the liquid nitrogen, which is typically at a temperature of the order of -196 ° C, so as to break all or part of the caesifable layer may be formed by vaporization of liquid nitrogen to nitrogen gas in contact with the hot elements , and thus significantly improve the cooling and / or lubrication of the machining area compared to a use of liquid nitrogen alone.
• a cryogenic fluid in the liquid state that is to say the liquid nitrogen, which is typically at a temperature of the order of -196 ° C
• machining area and “heating zone” are used interchangeably to designate the region of the workpiece that is likely to be heated due to the actual machining.
• the liquid nitrogen is nitrogen (chemical designation: N 2 ) in the liquefied state, that is to say at a temperature typically of the order of -190 to -200 ° C, in particular to -196 ° C at atmospheric pressure (1 atm).
• N 2 nitrogen
• the purity of the liquid nitrogen is typically at least 99% by volume, i.e. it is not excluded that the nitrogen may contain unavoidable impurities.
• the method of the invention may include one or more of the following features:
• a cooling jet formed of liquid nitrogen and 10 to 70% by mass of C0 2 particles in solid form is dispensed.
• the cooling jet formed of liquid nitrogen and solid particles is at a pressure between 1 and 400 bar.
• the mixture of liquid nitrogen and solid particles is carried out in situ simultaneously or just before it is dispensed.
• the liquid nitrogen and the solid particles are distributed by one or more distribution nozzles.
• the machining is a drilling or cutting.
• the workpiece is formed of a metallic, ceramic, composite or plastic material.
• the workpiece is formed of a metallic material chosen from carbon steel, aluminum and its alloys, stainless steel, nickel and / or chromium alloys, and titanium and titanium alloys .
• the invention also relates to a machining installation comprising a machining tool and at least one dispensing nozzle in fluid communication with a source of cooling fluid, characterized in that the source of cooling fluid is suitable. and designed to feed the nozzle into a mixture of liquid nitrogen and solid C0 2 particles.
• Figure 1 shows a first embodiment of the invention and Figure 2 shows a second embodiment of the invention.
• Figure 1 illustrates a first embodiment and implementation of the machining method of the invention.
• a part 2 to be machined for example a metal or plastic part, is subjected to a machining operation, such as drilling, cutting or the like, by means of a machining tool 1, by example a rotary or oscillating tool, such as a strawberry.
• the zone or region 5 of the part 2 machined by the tool 1 undergoes a heating due to friction or the like occurring between the tool 1 and the part 2.
• all or part of the machining zone 5, which can be heated, is cooled by distributing liquid nitrogen at the level of said machining zone 5 and possibly also at the level of the tool 1 .
• a single jet 6 formed of liquid nitrogen mixed with C0 2 particles in solid form, typically a mixture of liquid nitrogen containing from 10 to 70% by weight of C0 2 particles in solid form, that is to say in the form of dry ice.
• This liquid nitrogen / CO 2 solid mixture is produced in situ, either in the distribution nozzle 3 which delivers the single jet 6, or upstream of said nozzle 3, for example in a mixing chamber connected, on the one hand, to a source of solid C0 2 and, secondly, a source of liquid nitrogen.
• FIG. 2 illustrates a second embodiment of the invention similar to that of FIG. 1 but in which the injection of liquid nitrogen and solid CO 2 particles is done using two injection nozzles 3, 4, for example here a first nozzle 3 arranged vertically and a second nozzle 4 arranged horizontally.
• the two nozzles 3, 4 can each dispense a liquid nitrogen / solid CO 2 mixture.
• one of the nozzles 3,4 can dispense liquid nitrogen and the other the solid CO 2 particles, mixing them in situ at the machining zone 5 to be cooled.
• the C0 2 particles used are solid at cryogenic temperature, that is to say typically at less than -150 ° C but become gaseous as soon as their temperature exceeds about -78 ° C, therefore a fortiori at room temperature.
• the C0 2 has a thermal conductivity at -196 ° C, which is the temperature of the liquid nitrogen, of the order of 0.05 W / (mK), therefore much higher than that of the nitrogen gas at the same temperature, namely 0.0145 W / (mK).
• the solid C0 2 in addition to its role of disintegrating the coking layer forming at the interface between the liquid nitrogen and the surface of the part 2, has also a thermal bridge effect and provides frigories for cooling also the machining area.
• the C0 2 will not create secondary waste to be reprocessed, nor degrade or hinder the actual machining process, because of its low abrasive effect.
• a premix of CO 2 is prepared in the form of dry ice and liquid nitrogen before injection to the machining zone 5. Under these conditions, the solid CO 2 particles are cooled to about -196 ° C. that is, at the temperature of the liquid nitrogen in which they are.
• the liquid nitrogen / solid CO 2 mixture according to the invention must contain more than 10% by weight of CO 2 to obtain a notable effect of CO 2 and a maximum of 70% by weight of CO 2 in order to maintain a mixing viscosity compatible with the injection processes.
• the flow of cryogenic liquid nitrogen / CO 2 solid mixture can be injected vertically as illustrated in Figure 1 but also horizontally or at a given angle between the horizontal position and the vertical position.
• the injection angle most suitable for a given machining can easily be determined empirically, on a case by case basis, particularly as a function of the configuration of the part and / or the tool, of the efficiency of the cooling to be obtained. ..
• the piece 2 to be machined and cooled may be formed of a metallic material, ferrous or non-ferrous, such as stainless steel, titanium or an alloy thereof, an alloy based on chromium or nickel, such as an Inconel, or a non-metallic material, in particular a plastic polymer, such as a ductile high-performance type plastic (PPS, PI, PAL, etc.) or a ceramic.
• a metallic material ferrous or non-ferrous, such as stainless steel, titanium or an alloy thereof, an alloy based on chromium or nickel, such as an Inconel, or a non-metallic material, in particular a plastic polymer, such as a ductile high-performance type plastic (PPS, PI, PAL, etc.) or a ceramic.
• cooling is carried out in the machining zone 5 but it is also possible to simultaneously cool all or part of the tool 1 itself by means of the liquid nitrogen / CO 2 solid mixture.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Auxiliary Devices For Machine Tools (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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ID=43984151

Family Applications (1)

Country Status (7)

Cited By (5)

Families Citing this family (10)

Citations (8)

Family Cites Families (4)

• 2010
  • 2010-10-22 FR FR1058638A patent/FR2966371B1/fr not_active Expired - Fee Related
• 2011
  • 2011-10-06 ES ES11779806.6T patent/ES2531848T3/es active Active
  • 2011-10-06 EP EP11779806.6A patent/EP2629931B1/fr active Active
  • 2011-10-06 JP JP2013534360A patent/JP2013543797A/ja active Pending
  • 2011-10-06 US US13/880,775 patent/US20130209186A1/en not_active Abandoned
  • 2011-10-06 WO PCT/FR2011/052331 patent/WO2012052650A1/fr not_active Ceased
  • 2011-10-06 CN CN201180050828.2A patent/CN103180093B/zh active Active

Patent Citations (8)

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